Cellulose is used for paper, woody structural materials, fiber, cloths, food, cosmetics, and pharmaceuticals, as well as it is utilized as energy. Therefore, cellulose is industrially useful and valuable. Cellulose is capable of forming a variety of crystalline structures, and hence it is expected to develop a new material by controlling enzymes involved in biosynthesis of cellulose. The cellulose-related industry has been hitherto directed to such cellulose products that have been already produced, in which there has been no trial to develop a new material based on an aspect of biosynthesis. The mechanism of disease action, which is exerted by pathogenic microorganisms on plants, often results from the inhibition on cellulose biosynthesis as in Pyricularia oryzae (P. oryzae). Therefore, the addition of disease resistance to the cellulose biosynthesis mechanism is agriculturally applicable and valuable. Further, cellulose is the most abundant organic compound on the earth, and it is a sink in which the largest amount of CO.sub.2 in the atmospheric air is fixed. Therefore, the genetic improvement of cellulose biosynthesis enzymes is also applicable to the industry which is directed to the control of CO.sub.2 in the atmospheric air based on the use of cellulose as the sink.
In recent years, cDNA's originating from fiber cells of cotton plant have been randomly sequenced, and it has been reported that full length CelA1 and partial length of CelA2 probably represent cDNAs of cotton plant cellulose synthase, in view of the homology to bacterial cellulose synthase gene (bacterial BcsA) (Pear et al., Proceeding of National Academy of Science, USA (1996) 93 12637-12642). The binding ability to UDP-glucose has been demonstrated for CelA1. However, as for CelA2, the homology has been merely demonstrated for the C-terminal amino acid sequence.